In recent years, in semiconductor circuit elements that conduct a large current and include high-breakdown-voltage components, decreasing gate-to-drain capacitance has been demanded to lower the on-resistance and decrease switching losses. The on-resistance of semiconductor circuit elements is caused principally by drift resistance within drift layers and channel resistance within channel areas. Attempting reduced on-resistance is a crucial issue.
One known example is a semiconductor circuit element in which the gate electrode is formed inside a trench extending perpendicularly to the semiconductor substrate. In such semiconductor circuit elements, technology for reducing channel resistance by narrowing the spacing between a plurality of the trenches is known.
Narrowing the trench spacing, however, means that the drift-layer regions are also narrowed and the drift resistance rises. This is a problem. Consequently, with technology to date, attaining reduced drift resistance while also attaining reduced channel resistance is not easy.